/**
 * PKCS7
 * 
 * An equivalent padding implementation of PKCS7 based on the provided PKCS5 code.
 * Copyright (c) 2007 Henri Torgemane
 * 
 * See LICENSE.txt for full license information.
 */
package com.hurlant.crypto.symmetric
{
    import flash.utils.ByteArray;

    public class PKCS7 implements IPad
    {
        private var blockSize:uint;

        public function PKCS7(blockSize:uint = 0) {
            this.blockSize = blockSize;
        }

        public function pad(a:ByteArray):void {
            var c:uint = blockSize - a.length % blockSize;
            for (var i:uint = 0; i < c; i++) {
                a[a.length] = c;
            }
        }

        public function unpad(a:ByteArray):void {
            var c:uint = a.length % blockSize;
            if (c != 0) throw new Error("PKCS#7::unpad: ByteArray.length isn't a multiple of the blockSize");
            c = a[a.length - 1];
            for (var i:uint = c; i > 0; i--) {
                var v:uint = a[a.length - 1];
                a.length--;
                if (c != v) throw new Error("PKCS#7:unpad: Invalid padding value. expected [" + c + "], found [" + v + "]");
            }
            // that is all.
        }

        public function setBlockSize(bs:uint):void {
            blockSize = bs;
        }

    }
}
